Mechanical impedance in horticultural substrates

The penetration power of the roots into the soil has been studied in relati on to field crops but not to container media. In this work the mechanical i mpedance of sand, perlite, peat, coir and commercial mixtures were evaluate d: Fafard no 2, Fafard 2P, Jiffy 7 and Oasis. Dry and saturated samples wer e analyzed under four levels of compactation. Jiffy 7 and Oasis were analyz ed only in the original density of the manufactured products. The impedance was measured by a metal probe and a digital micropenetrometer. The penetra tion pressure is correlated to the level of compactation of the media, with significant interaction between compactation and moisture level.